Photoexcitations in poly(p-phenylenevinylene) aggregates

Abstract

Photo-induced electronic excitations of poly(p-phenylenevinylene) (PPV) aggregates are simulated and characterized using a recently developed linear-scaling localized-density-matrix (LDM) method. The intra-and inter-chain components of excitations are analyzed and quanti®ed for dierent inter-chain distances. The excitations for the absorption and luminescence in PPV ®lm and its derivatives are identi®ed and are found analogous to those of H-aggregates. Their energy shifts upon aggregation are determined mainly by the inter-chain kinetic energy reduction and the Coulomb interaction of the electron±hole pair. It is concluded that the luminescence is caused by the intra-chain electron±hole pairs. Ó

Irinotecan and uridine diphosphate glucuronosyltransferase 1A1 pharmacogenetics

“…However, the fluorescence spectrum in thin film exhibited an obvious bathochromic shift with a broad emission band at long wavelength centered at 610 nm. This suggests that significant aggregation and excimer exist because of the intermolecular π–π stacking between the rigid PPV backbones, similar to the previous reports for other PPVs 56–59. We did not observe the significant difference in the UV–vis and PL spectra between the three polymers on the films, indicating that the different alkyl chain substituents do not have significant effect on their fluorescence spectra in solid state.…”

Theoretical Investigation on Electronic Transition of Tris(8‐quinolinolate) Aluminum Grafted on Poly(p‐phenylenevinylene) Units with the Localized‐density‐matrix Method

“…12 Therefore, PPV has been extensively studied due to its high fluorescent yield and stability. [13][14][15][16][17] Some researches attempted to obtain perfect emission spectra by changing the substitution of PPV chain in order to improve its optical properties. For example, as early as in 1933, Greenham and his colleagues 18 synthesized a fluorescent poly(cyanoterephthalylidene) (CN-PPV) with fairly good solubility, which has lower energy gap and can enhance EL efficiency.…”

“…However, the localized density matrix theory (LDM) had been developed by Chen group. [14][15][16][24][25][26] Its advantages lie in decreasing the computational time since the number of matrix elements is reduced in the density matrix in the equation of motion. So the LDM method is the linear-scaling quantum chemistry method by simulating molecular excited state properties, such as optical, electric and magnetic properties, even in the large molecular systems.…”

Localized-density-matrix calculation of circular dichroism spectrum of optically active molecule

“…They were of reasonable success, provide the insights into the physical interpretation of the CD of given structures, and explain the reason why the CD spectra are used to determine the protein secondary structures. Recently the localized-density-matrix (LDM) method has been developed to evaluate the ground and excited state properties of very large systems [28][29][30][31][32][33][34][35][36][37]. It is based on the truncation of reduced single-electron density matrices, and thus, its computational time scales linearly with the system size.…”

“…It is based on the truncation of reduced single-electron density matrices, and thus, its computational time scales linearly with the system size. The LDM method has been generalized to include the nonorthogonal basis set [32], has been implemented with the semiempirical Hamiltonians like PPP [38], CNDO/S [39] and PM3 [40], and has subsequently been used to calculate the optical properties of polyacetylene [28][29][30][31]33,36], carbon nanotubes [33,34] and poly(p-phenylenevinylene) (PPV) aggregates [35,37]. In this work, we develop an efficient quantum mechanical method to evaluate the CD spectra of large molecular systems and their nonlocal response tensors.…”